Misc. Diagnostic tests/Statistics/PT and Sonographer Safety

Question 1

what is the gold standard in arterial evaluation

Answer 1

arteriography

Question 2

describe how arteriography is performed

Answer 2

percutaneous puncture of an artery

catheter inserted and positioned into the vessel of interest

radiopaque contrast (dye) is injected into the vessel and is carried with the moving blood

fluoroscopy images the contrast and provides a picture of the lumen

catheter is removed, and the puncture site is controlled with manual pressure, pressure dressing or a vascular closure device

Question 3

what are limitations for arteriography

Answer 3

contraindication due to contrast allergy or renal insufficiency - dye is cleared through the kidneys and may be nephrotoxic

given the lumen is viewed in two planes, the disease may be under or overestimated

Question 4

what is magnetic resonance angiography (MRA)

Answer 4

employs a strong magnetic field and radio frequency energy to produce images in multiple planes

flowing blood is well distinguished from stationary soft tissues without contrast

Question 5

what are limitations to magnetic resonance angiography

Answer 5

presence of pacemakers, metallic clips, and monitoring equipment can preclude its use

can overestimate disease due to either slow flow or turbulence

expensive

patients with claustrophobia may limit its use

Question 6

what is a computerized tomography angiography (CTA)

Answer 6

employs ionizing radiation (x ray) to obtain cross sectional images of the soft tissue and blood vessels, especially good for aorta and peripheral arteries

IV contrast can provide a more detailed evaluation of some structures

Question 7

wha are limitations to CTA

Answer 7

patient motion may blur the images

presence of pacemakers or metallic clips may result in shadows

limited application in small vessels

single plane use

expensive

significant ionizing radiation exposure

Question 8

what is the gold standard for venous evaluation

Answer 8

duplex scanning

Question 9

describe contrast venography

Answer 9

radiopaque dye or contrast injected into veins and x ray image depicts the vein lumen by showing the contrast

Question 10

what are limitations to contrast venography

Answer 10

difficult technique and interpretation

expensive

invasive, carries a small risk of causing venous thrombosis

uncomfortable for patient

contraindication for patients with contrast allergies and severe PAD due to the risk of necrosis from contrast extravasation outside the vein into the tissues

Question 11

what are the two types of venography techniques

Answer 11

ascending venography and descending venography

Question 12

describe ascending venography

Answer 12

radioplaque contrast injected into a vein o nth dorsum of the foot

serial x rays are obtained as the contrast passes through the veins to identify filling defects, anatomic variations and collateral development

Question 13

describe depending venography

Answer 13

evaluates retrograde flow resulting from valvular incompetence

patient in upright position

radiopaque is injected into the CFV

serial x rays obtained to determine if contrast flows retrograde down the leg

can determine the relative amount of reflux and location of incompetent valves

Question 14

true positive

Answer 14

our test indicates disease (positive) and is correct (true)

Question 15

true negative

Answer 15

our test indicates normal (negative) and is correct (true)

Question 16

false positive

Answer 16

out test indicates disease (positive) and is incorrect (false)

Question 17

false negative

Answer 17

our test indicates normal (negative) and is incorrect (false)

Question 18

statistics rule

Answer 18

look at OUR test first to determine + or - and then at the gold standard to determine true or false

Question 19

sensitivity

Answer 19

the ability of a test to detect disease when present

sensitivity = true positive / true positive + false negative

Question 20

specificity

Answer 20

the ability of a test to identify normalcy (NO DISEASE PRESENT)

specificity = true negative / true negative + false positive

Question 21

positive predictive value (PPV)

Answer 21

percentage of positive studies that are correct

PPV = true positive / true positive + false positive

Question 22

negative predictive value (NPV)

Answer 22

percentage of negative studies that are correct

NPV = true negative / true negative + false negative

Question 23

accuracy

Answer 23

percentage of ALL studies that are correct

accuracy = true positive + true negative / total number of exams

Question 24

accuracy lies between

Answer 24

sensitivity and specificity

positive and negative predictive values

ex
sensitivity = 85%
specificity 90%
accuracy is 87% (lies in between)

positive predictive value 92%
negative predictive value 82%
accuracy is 87% (lies in between)

Question 25

screening

Answer 25

likelihood of detecting these disorders at an early stage

Question 26

testing

Answer 26

determine if disease is present or absent

Question 27

SNOUT

Answer 27

sensitivity rules negative out

good for screening - you want a screening test to be highly sensitive, so you do not tell the person they do NOT have a disease, even if that meant picking up some false negatives

Question 28

SPIN

Answer 28

specificity rules positive in

good for confirmatory testing - after you’ve identified all the positives by your highly sensitive screening test, you’d want a confirmatory test to be highly specific, so you do not tell the person they have disease when they do NOT

Question 29

what is the grid for statistics

Answer 29

gold standard results always on top
study exam results always on the left
top row = positives
bottom row = negatives

A (true positive) / B (false positive)
C (false negative) / D (true negative)

the gold standard is the test that we compare our results to and is always assumed to be 100% correct

Question 30

how to calculate sensitivity using grid

Answer 30

A / (A+C)

Question 31

how to calculate specificity using grid

Answer 31

D / (D+B)

Question 32

how to calculate PPV using grid

Answer 32

A / (A+B)

Question 33

how to calculate NPV using grid

Answer 33

D / (D+C)

Question 34

how to calculate overall accuracy using grid

Answer 34

A+D / (A+B+C+D)

Question 35

NOT A CARD BUT A NOTE

Answer 35

do example on page 288

Question 36

what is the rule of 30s

Answer 36

shoulder hyperabduction >30
scanning patient with body was index >30
duration (sonographer age >30 y/o or scanning >30 years)